Chain with endless braided chain-link

ABSTRACT

A chain includes a plurality of interconnected chain links, wherein at least one of the chain links comprises a Turk&#39;s head braided core having at least two consecutive turns of at least one primary strand. The at least one primary strand includes polymeric elongated elements having a tenacity of at least 1.0 N/tex.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.16/306,905 filed on Nov. 30, 2018 (now U.S. Pat. No. 11,181,169), whichin turn is the U.S. national phase of International Application No.PCT/EP2017/055212 filed Mar. 6, 2017 which designated the U.S. andclaims priority to EP Patent Application No. 16172945.4 filed Jun. 3,2016, the entire contents of each of which are hereby incorporated byreference.

FIELD

The invention relates to a chain comprising multiple chain-links, atleast one chain-link comprising a load-bearing core comprising a firstprimary strand, the first primary strand comprising polymeric elongatedelements wherein the polymeric elongated elements have a tenacity of atleast 1 N/tex. The invention also relates to an endless shaped elementsuitable as a load bearing core for the chain of the invention.

BACKGROUND AND SUMMARY

A chain should desirably be capable of transmitting forces under allkinds of circumstances and environmental conditions, often for aprolonged period of time, without the chain being affected in any way,such as by breaking, fraying, cut, fatigue, ageing, corrosion, damaging,and so on. Other requirements may also be important. During use in theabove-mentioned operations, chains are subjected to substantial wear andtear conditions which may lead to extensive abrasion of the chain.Chains should therefore be durable. Chains moreover should not only bestrong and durable, but at the same time be as lightweight as possible,in order not to unduly increase health risks during handling or reducepayload, this requirement being even more important for heavier,stronger chains.

A chain with low maximum break load comprising a plurality ofinterconnected links comprising polymeric elongated elements, is knownfrom WO2008/089798. WO2008/089798 discloses chains comprising engaginglinks of ultra-high molecular weight multifilament yarns. The links areconstructed as multiple turns of yarns or multiple turns of strapscomprising yarns. The chains described in WO2008/089798 have goodtenacities and abrasion properties. Yet WO2013186206 identified in itscomparative experiments that high maximum break load chain-links withsuch constructions suffer a substantial efficiency loss. Accordingly,WO2013186206 describes chain-links with increased efficiencies ascompared to the chain-links of WO2008/089798. WO2013186206 provides anefficiency improvement by an endless shaped element comprising a stripthat is wound about itself while comprising a 180° twist, forming aso-called Moebius loop. Herewith the efficiency of said endless shapedelements is improved, but the authors are silent about the strength ofthe therein described chains comprising such chain-links. Furthermore EP1 587 752 describes round slings consisting of a load-bearing corecontaining at least two turns of a load bearing rope of which theterminal ends are spliced.

The object of the present invention is to provide chain very wellcapable of transmitting forces and moreover showing improved efficiency,also referred to as strength retention, of the employed polymericelongated element as compared to the chains known in the art.

This object is achieved according to the invention by a chain comprisinga plurality of interconnected chain-links wherein at least onechain-link comprises a braided core comprising a first primary strandcomprising a polymeric elongated element wherein the polymeric elongatedelement has a tenacity of at least 1.0 N/Tex, characterized in that thebraided core comprises at least 2 consecutive turns of said firstprimary strand.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a chain link according to the embodimentdescribed hereinbelow by Example 1.

DETAILED DESCRIPTION

A chain according to the invention shows an unexpectedly increasedefficiency in that the chain retains more from the tenacity of thecomprised elongated elements, especially for high maximum break loadchains. Further the chain maintains or even increases its durabilityover comparative prior art and has a substantially improved damagetolerance in that a number of primary strands may be ruptured withoutthe breakage of the chain. Moreover, the braided link according to thepresent invention can be made at ratios of chain link thickness to chainlink length that are larger than said ratios for laid links of prior artrope constructions. In addition, there is hardly no upward size limit inproduction, so strong chains and chain links with large dimensions arepossible to produce according to the present invention. Furthermore, thechain links made from the yarns according to the prior art, e.g. asdisclosed in WO2008/089798 contain all fibers of the yarn arranged inload direction, whereas the fibers in the braided link in the chainaccording to the present invention may not be all arranged in loaddirection, i.e. the fibers are not over the majority of their length.Also, the core of the chain link of the present invention may containfibers arranged under an angle with the load direction. Therefore, thestrength, i.e. tenacity of the chain according to the present inventionis surprisingly much higher than the strength, i.e. tenacity of thechains according to prior art, as the skilled person in the art wouldexpect to obtain a chain having lower strength for chains containingfibers that are not arranged in load direction.

Preferably, the static strength of the chain of the invention is atleast 10 kN, more preferably at least 50 kN, even more preferably atleast 100 kN, yet even more preferably at least 300 kN or at least 500kN, yet even more preferably at least 1000 kN, yet even more preferablyat least 10000 kN, yet even more preferably at least 50000 kN, yet evenmore preferably at least 100000 kN, yet even more preferably at least150000 kN, yet even more preferably at least 500000 kN, most preferablyat least 10⁶ kN. By static chain strength is herein understood thestrength of the chain when the chain is subjected to a static load.

The chain structure may be any structure known in the art. The chainaccording to the invention is characterized in that the chain comprisesinterconnected chain-links. Such chains are easily tailored according totheir needs. For instance, their length is easily adjusted by adding orremoving links. Adding links is for instance carried out by braidingseveral windings of a primary strand through the opening of an existingchain-link, and optionally securing the newly made chain-link byfastening the ends of the primary strand. Also side chains may easily beadded to the (main) chain in a similar manner. This embodiment of thechain according to the invention also has an improved strength, sincethe links are endless, and therefore do not have many cut ends.

The chain-links may also be interconnected by all means known in theart. Preferably the interconnected chain-links are interconnected byinterlacing. In still another embodiment the chain according to theinvention is characterized in that the links are interconnected byconnecting means which are preferably ring shaped. In such anembodiment, the connecting means preferably comprise UHMWPE elongatedelements. They may be attached to the connecting means by any suitablemeans, but preferably by stitching. In a preferred embodiment, the ringshaped connecting means may have different shapes as for example acircle, an oval, a triangular or a rectangular shape and may be made ofany suitable material, including metal.

The elongated element is preferably a fiber, a yarn, and especially amultifilament yarn. By fiber is herein understood an elongate body, thelength dimension of which is much greater than the transverse dimensionsof width and thickness. Accordingly, the term fiber includes filament,bundle, ribbon, strip, band, tape, and the like having regular orirregular cross-sections. The fiber may have continuous length, known inthe art as filament, or discontinuous length, known in the art as staplefiber. Staple fibers are commonly obtained by cutting orstretch-breaking filaments. A yarn for the purpose of the invention isan elongated element containing many fibers. A multifilament yarn forthe purpose of the invention is an elongated element containing manyfilaments.

It was found that the mechanical properties of the chain according tothe invention, in particular its strength can be improved bypre-stretching the chain or each of the chain-links prior to its usebelow the melting point of the polymer. For polyethylene elongatedelements the pre-stretching of the chain or chain-links is performedbetween 80-140° C., more preferably between 90-130° C.

In one embodiment, the core of the chain-link or the chain according tothe invention is pre-stretched at a temperature below the meltingtemperature T_(m) of the polymer, by applying a static load of at least5%, more preferably at least 10%, and most preferably at least 15% ofthe breaking load of the core or the chain for a period of time longenough to achieve a permanent deformation of the core of between 2 and20%, and more preferably between 5 and 10%. By permanent deformation isherein understood the extent of the deformation from which the braidedcore does not recover when substantially load free.

In another embodiment, the chain according to the invention is subjectedto a number of load cycles. Preferably, the number of cycles ranges from2-25, more preferably from 5-15, and most preferably from 8-12, wherebythe maximum load applied is lower than 45% of the breaking load of thechain, more preferably lower than 35% of the breaking load of the chain,and most preferably lower than 25% of the breaking load of the chain. Itis possible according to the invention to unload the chain during loadcycling. In a preferred method however, the minimum load applied is atleast 1%.

By plurality of chain-links is meant in the context of the presentinvention at least 2 chain-links that are interconnected as describedfurther above. Typically for a chain a plurality is at least 3,preferably at least 4 and most preferably at least 5 interconnectedchain-links. Chains with increasing numbers of links have increasedversatility in their applications.

At least one chain-link of the chain according to the inventioncomprises a braided core comprising at least 2 consecutive turns of afirst primary strand, whereas the braided core preferably comprisesfurther consecutive turns of said first primary strand. The braided coremay also comprise single or multiple turns of further (second, third,etc.) primary strands. By turns in the context of the present inventionis understood that a length of a primary strand completes a loop orrevolution within the braided core of the chain-link, said primarystrand being a constituting part of the braided core or even that theprimary strand and the optional further primary strands form the braidedconstruction of the core. In this context turn may be synonym to loop orrevolution. By consecutive turns is understood that said length ofprimary strand after completion of a first turn is directly engaged in asecond turn within the braided core. Accordingly, the braided core orbraided cores of the chain of the invention have a cross-sectioncomprising a number of cross-sections of primary strands originatingfrom the same or different primary strands. In a preferred embodimentthe cross-section of the braided core substantially consists of thecross-sections of primary strands originating from the same or differentprimary strands. Preferably the braided core has a cross-sectionequivalent to at least 3, preferably at least 4, more preferably atleast 6 cross-sections of the first primary strand. Accordingly, in apreferred embodiment, the braided core comprises at least 3, preferablyat least 4 and more preferably at least 6 consecutive turns of the firstprimary strand. The presence of increased numbers of consecutive turnsof first primary strand in the braided core increases the damagetolerance of the braided core and the chain. The more consecutive turnsof a specific primary strand the braided core contains, the more robustand damage resistant the braided core is. By increasing said number ofconsecutive turns of a primary strand in the braided core the resistanceto slippage of the chain-link and chain improves. This braided nature ofall the consecutive turns within each link lowers by each turn theresidual load on the end connection of both remaining ends of the strandsignificantly. That means, that spliced, stitched, glued, welded orknotted end connection of both ends of the strand are not needed toprevent slipping, since the entire link forms a whole splice in its own,but can be still applied to prevent any slipping at all. There is noupper limit to the number of turns of the same primary strand in thebraided core construction but high numbers will increase the level ofcomplexity of the braided core and render the manufacturing moreexpensive. Preferably the number of turns of the same primary strand inthe braided core is at most 24, more preferably at most 18 and mostpreferably at most 12.

The at least one braided core of the chain according to the inventionmay comprise one or more further primary strands, each further primarystrand forming a single turn or multiple consecutive turns in thebraided core. Said further primary strands allow an increased designflexibility at reduced manufacturing effort. Preferably the number offurther primary strands in the braided core is at most 11, morepreferably at most 5, whereas more preferably the total number ofprimary strands, including the first primary strand, in the braided coreis 1, 2, 3, 4 or 6. It was identified that said preferred number ofprimary strands represents a good compromise between manufacturingadvantages and damage tolerance of the chain of the invention.

In a preferred embodiment, the braided core comprises one or morefurther primary strands wherein said braided core comprises at least 2consecutive turns of each of the one or more further primary strands,preferably at least 3 consecutive turns, more preferably at least 4 andmost preferably at least 6 consecutive turns of each of the one or morefurther primary strand. Accordingly, in said preferred embodiment abraided core of the chain of the invention may comprise a total of 2, 3,4 or 6 distinct primary strands, whereby at least 2, preferably all, ofsaid primary strands form at least 2, preferably at least 3 turns, morepreferably at least 4 and most preferably at least 6 consecutive turnsof the braided core construction.

Adding the number of turns of each of the distinct primary strands willprovide the total number of turns of primary strands present in thebraided core. In a preferred embodiment, the ratio of the total numberof primary strand turns in the braided core to the number of primarystrands in the braided core is at least 2, preferably at least 3, morepreferably at least 4 and most preferably at least 6. The higher saidratio the more damage tolerant the chain according to the invention is.

In a preferred embodiment the first primary strand comprises a firstpolymeric elongated element and the one or more further primary strandscomprises one or more further polymeric elongated element, whereby thepolymers of the first and the one or more further elongated elements areof the same type, preferably the first primary strand and the one ormore further primary strands comprise polymeric fibers of the same type,even more preferably the first primary strand and the one or morefurther primary strands comprise polymeric yarns of the same type.

In an alternative preferred embodiment the first primary strandcomprises a first polymeric elongated element and the one or morefurther primary strands comprises one or more further elongatedelements, wherein at least one of the one or more further elongatedelements differ from the first polymeric elongated element, preferablythe at least one of the one or more further elongated element differfrom the first polymeric elongated element by at least one propertyselected from the list consisting of material, tenacity, yarn titer,filament titer or creep rate.

The core of the chain-link of the chain according to the invention isbraided and may have any braiding structure known to the skilled personas for example disclosed for braided ropes in Chapter 3 of the Handbookof fibre rope technology (eds McKenna, Hearle and O'Hear, WoodheadPublishing Ltd, ISBN 1 85573 606 3). Such structure may for example besingle braids in a twill or plain weave fashion, plain or hollow, doublebraids also called braid on braid or solid braids, depending on theproperties the chain should have. In the context of the presentinvention a core being braided from primary strands is also referred toas braided core.

Braided ropes known in the art are composed of a plurality of distinctprimary strands interlaced with each other forming the braidedconstruction of the rope. Slings or endless shaped articles, made fromsuch braided ropes are also well known, whereby a length of a braidedropes is formed into a sling by joining the 2 ends of a said length ofbraided rope by for example knotting or splicing. In contrast to thebraided core of the chain-link of the chain of the invention, suchspliced braided ropes comprise a plurality of primary strandssubstantially equal to the number of primary strands present in theoriginal rope whereby the splice, the section where the ends of the ropeoverlap, has a length of about 15 to 20 times the diameter of the rope.Especially for chain-links such splice are prohibitively long and thick,especially for large diameter ropes and/or small chain-links. Althoughthe braided core according to the invention may have an appearancesimilar to the braided sling described here above, a doubling of titreover 15-20 times its diameter will be absent.

The braided core of the chain-link of the chain according to theinvention can be of a construction wherein the braiding period, alsoreferred to as the pitch or pitch length (L) related to the diameter (D)of the rope, is not specifically critical; suitable braiding periods arein the range of from 3 to 30 L/D ratio. A higher braiding period resultsin a looser braided core having higher strength efficiency, but which isless robust and less damage tolerant. Too low a braiding period reducestenacity of the braided core too much. Preferably therefore, thebraiding period is about 5 to 20, more preferably 6 to 15 L/D ratio.

The braided core of the chain-link of the chain according to theinvention can have a diameter (D) that varies between wide limits.Smaller diameter cores, for example in the range of from about 1 to 10mm, are typically applied as chains for securing cargo duringtransportation. Large diameter, or heavy-duty chains, typically have adiameter of at least 10 mm. In case of a braided core with an oblongcross-section, it is more accurate to define the size of a round core byan equivalent diameter; that is the diameter of a round core of samemass per length as the non-round braided core. The diameter of a braidedcore in general, however, is an uncertain parameter for measuring itssize, because of irregular boundaries of braided cores defined by theprimary strands. A more concise size parameter is the linear density ofa braided, also called titer; which is the mass per unit length. Thetiter can be expressed in kg/m, but often the textile units denier(g/9000 m) or dTex (g/10000 m) are used. For large diameter cores theunit of MTex, equivalent to kg/m, is used. Diameter and titer areinterrelated according to the formula D≈(4*t/(π*10*ρ*v))^(0.5), whereint is the titer in dTex, D is the average diameter in mm, ρ is thedensity of the filaments in kg/m³, and v is a packing factor (normallybetween about 0.7 and 0.9). Nevertheless, it is still customary in therope business to express rope size in diameter values or alternativelyfor non-circular cross-section in a cross-sectional surface area. Thechains according to the invention preferably have at least on braidedcore with a cross-section of between 5 mm² and 5 dm², preferably between10 mm² and 3 dm², more preferably between 50 mm² and 100 cm².Preferably, the chains according to the invention are high load carryingchains having an equivalent diameter of at least 10 mm, more preferablyat least 15, 20, 25, or even at least 30 mm, since the advantages of theinvention become more relevant the larger the braided core.

The inventors identified that by the braided core construction describedherein chain-links and especially chains have been made available withtenacity properties superior to the synthetic chains known to date.Therefore one embodiment of the invention concerns the braided endlessshaped element suitable to be used as a braided core for a chain-link ofthe invention wherein the braided endless shaped element comprises atleast 2 turns of the first primary strand comprising a polymericelongated element wherein the polymeric elongated element has a tenacityof at least 1.0 N/Tex. Such endless shaped article may also be referredto as a braided sling or braided endless article and may becharacterized by any of the preferred embodiments as further disclosedherein.

Braided cores with diameters, cross-sectional surface areas or titercomprising the polymeric elongated element may provide chains andchain-links with high strength. Therefore one embodiment of the presentinvention are chains according to the invention wherein the chain has atenacity of at least 0.50 N/tex, preferably the chain has a tenacity ofat least 0.55 N/tex, more preferably at least 0.60 N/tex, even morepreferably 0.65 N/tex and most preferably at least 0.70 N/tex. In afurther embodiment of the invention, the braided endless shaped elementshave a tenacity of at least 0.90 N/tex, preferably at least 1.10 N/tex,more preferably at least 1.20 N/tex and most preferably at least 1.30N/tex. Herein the tenacity of the chain and cores are expressed as themaximum break load divided by sum of the titers of the 2 legs of thebraided core.

It was also observed by the inventors that the chains according to theinvention have a higher retention of the tenacity of the underlyingpolymeric elongated element then known hitherto, also referred to aschain efficiency, whereby chain efficiency is expressed as the ratiobetween yarn tenacity to chain tenacity. Such effect was speciallyobserved for chains with a very high strength and high titer. Therefore,one embodiment of the present invention relates to synthetic chains,preferably non-heat set synthetic chains, comprising a plurality ofinterconnected chain-links wherein at least one chain-link comprises apolymeric elongated element wherein the polymeric elongated element hasa tenacity of at least 1.0 N/tex wherein the chain has a tenacity (Ten)in N/Tex and a sum of the titer of the 2 legs of the chain-linkcomprising polymeric elongated elements (T) in MTex [kg/m], withTen≥f*T^(−0.05), wherein f is 0.50, preferably 0.55, more preferably0.60. It is known to the skilled person that the unit of f is such thatthe overall unit of the right side of the formula, i.e. f*T^(−0.05) isalso equal to N/Tex. This means that treatments for further increasingtenacity, e.g. heat setting may be less or even not necessary for chainsaccording to the present invention. Preferably the chains of thisembodiment have a breaking strength of at least 100 kN, more preferablyof at least 500 kN and most preferably of at least 1 MN.

In a preferred embodiment, the braided core comprising one or moreprimary strands of which the ends are connected by at least onefastening means. Although the construction inherently preventsdislocation and slipping of the primary strands, it was observed thatuse of fastening means further improves the stability of the braidedcore. Examples of fastening means in the context of the presentinvention are air entanglements, splices, stitches, glue, knots, bolts,heat sealing, rivets or the like.

In a preferred embodiment, the ends of the one or more primary strandsare connected by at least one fastening mean to each other. Such aconstruction may for example be achieved by adjustment of the lengths ofthe primary strands such that two ends of the primary strands overlapand applying an air entanglement, splice, stitching, gluing, knotting,bolting, heat sealing riveting or the like at said overlapping position.It was observed that a construction according to this embodimentresulted in an optimized efficiency of the braided core. By connected toeach other in the context of the present invention is meant both, thatthe two ends of one and the same primary strand are connected to eachother but also that two ends of distinct primary strands are connectedto each other. Both alternatives will have the same advantage ofstabilizing the braided structure of the core.

In a further preferred embodiment of the invention at least one end,preferably both ends of the first and/or any further primary strand in abraided core of at least one chain-link of the chain according to theinvention is buried within the centre of the braided construction. Suchpreference of the ends being in the inside of the braided constructionis independent from the ends being connected, alone or to each other byfastening means. The braided core will substantially provide the optionfor burying if the total number of primary strand turns is at least 8,preferably at least 12.

Optionally, at least one chain-link, preferably all chain-links furthercomprise a cover, wherein at least one primary strand or at least onebraided core, preferably all primary strands or all braided cores, maybe sheathed with a cover. Protective covers may have any constructionknown in the art and may comprise elongated elements as detailed above.Such a sheath is known for example from U.S. Pat. No. 4,779,411. If aprotective cover is used, its thickness is not to be taken into accountwhen determining the titer of the chain-link and/or its braided core.

Preferably, at least one of the braided cores of the chain according tothe invention comprises polymeric elongated elements that are at leastpartially coated with a thermoset or thermoplastic polymer. Anythermoset or thermoplastic polymer able to form a suitable compositewith the elongated elements may be used, whereas silicone resins andplastomers are the preferred thermoset or thermoplastic polymers,respectively. A chain according to this embodiment has chain-links whichdeform to a lesser extent when the chain is stretched. This isadvantageous when objects, such as hooks for instance, have to beattached to the chain especially when the chain is under load. Thecoating also offers further protection against damage development duringdynamic loading conditions for instance and limit the deterioration ofproperties during long term use.

The first primary strand and the optional one or more further primarystrands of the braided cores of the chain-link of the invention may havevarious constructions amongst which twisted or laid strand, a braidedstrand, a tendon of parallel yarns, or a woven strand. The variousconstructions, in particular the braided or laid strands, may comprisesub-strands that in turn may be bundles of parallel or twisted yarns.The nature of primary strands will substantially depend on theproperties and use of the chain. For heavy duty chains a braided ortwisted rope as primary strands will be preferred, providing a braidedcore with increased robustness.

For braided cores comprising at least one braided or laid primarystrands a special embodiment of the invention is that at least 2terminal ends of the at least one braided or laid primary strand areconnected together with a splice. Splices that may be employed will bewell known to the skilled person. This embodiment is especiallypreferred for braided cores with at most 12 total turns of primarystrands, preferably at most 8 total turns of primary strands. It wasobserved that at lower total numbers of turns of primary strands theincreased stability of the braided core and the reduced slippage of theprimary strands was especially pronounced.

In a further preferred embodiment of the invention the chain-linkcomprises a braided core wherein at least the first primary strand is alaid rope with preferably 3, 4, 6, or 6+1 sub-strands with a tuckedsplices between the ends of the laid primary strand, the advantage beingvery little slip in the connection.

The first primary strand of a braided core of a chain-link of the chainof the invention comprises a polymeric elongated element with a tenacityof at least 1.0 N/Tex. This can be an elongated element, preferably ayarn, of any high performance fibre material, like polyester, polyamide,aromatic polyamide (aramid), poly(p-phenylene-2,6-benzobisoxazole), orpolyethylene yarns. Preferably the elongated element is a high moduluspolyethylene (HMPE) yarn. HMPE yarn comprises highly-drawn fibres ofhigh-molecular weight linear polyethylene. High molecular weight (ormolar mass) here means a weight average molecular weight of at least400,000 g/mol. Linear polyethylene here means polyethylene having fewerthan 1 side chain per 100 C atoms, preferably fewer than 1 side chainper 300 C atoms, a side chain or branch generally containing more than10 C atoms. The polyethylene may also contain up to 5 mol % of one ormore other alkenes which are copolymerisable therewith, such aspropylene, butene, hexene, 4-methylpentene, octene.

In a yet preferred embodiment, the polymeric material of choice for theelongated element of the first primary strand is ultrahigh molecularweight polyethylene (UHMWPE). UHMWPE in the context of the presentinvention has an intrinsic viscosity (IV) of preferably between 3 and 40dl/g, more preferably between 8 and 30 dl/g. UHMWPE yarns are preferablymanufactured according to a gel spinning process as described innumerous publications, including for example WO2005066401, WO2012139934.This process essentially comprises the preparation of a solution of apolyethylene of high intrinsic viscosity, spinning the solution intosolutions filaments at a temperature above the dissolving temperature,cooling the solution filaments to below the gelling temperature to fromsolvent-containing gel filaments and drawing the filaments before,during or after at least partial removal of the solvent.

Advantages of a braided core comprising HMPE fibres include highabrasion resistance, good resistance against fatigue under flexuralloads, a low elongation resulting in an easier positioning, an excellentchemical and UV resistance and a high cut resistance.

The elongated elements, preferably the yarns, of the first primarystrand are of high strength, sometimes also referred to as high modulus.In the context of the present invention, the elongated element has atenacity of at least 1.0 N/Tex, preferably of at least 1.2 N/Tex, morepreferably at least 1.5 N/Tex, even more preferably at least 2.0 N/Tex,yet more preferably at least 2.2 N/Tex and most preferably at least 2.5N/tex. When the polymeric elongated element is a UHMWPE yarn, saidUHMWPE yarn preferably has a tenacity of at least 1.8 N/Tex, morepreferably of at least 2.5 N/Tex, most preferably at least 3.5 N/Tex.Preferably the polymeric elongated element has a modulus of at least 30N/Tex, more preferably of at least 50 N/Tex, most preferably of at least60 N/Tex. Preferably the UHMWPE yarn have a tensile modulus of at least50 N/Tex, more preferably of at least 80 N/Tex, most preferably of atleast 100 N/Tex.

The elongated elements of the one or more further primary strands mayindividually be selected from elongated elements comprising organic orinorganic fibres. Examples of inorganic materials suitable for producingelongated elements, especially fibres include steel, glass and carbon.Examples of organic synthetic materials suitable for producing theelongated elements, especially fibres include polyolefins, e.g.polypropyle (PP); polyethylene (PE); ultrahigh molecular weightpolyethylene (UHMWPE), polyamides and polyaramides, e.g.poly(p-phenylene terephthalamide) (known as Kevlar®);poly(tetrafluoroethylene) (PTFE); poly(p-phenylene-2, 6-benzobisoxazole)(PBO) (known as Zylon®); liquid crystal polymers such as for examplecopolymers of para hydroxybenzoic acid and para hydroxynaphtalic acid(e.g. Vectran®);poly{2,6-diimidazo-[4,5b-4′,5′e]pyridinylene-1,4(2,5-dihydroxy)phenylene}(known as M5); poly(hexamethyleneadipamide) (known as nylon 6,6),poly(6-aminohexanoic acid) (known as nylon 6); polyesters, e.g.poly(ethylene terephthalate), poly(butylene terephthalate), and poly(1,4cyclohexylidene dimethylene terephthalate); but also polyvinyl alcoholsand polyacrylonitriles. Also, combinations of elongated elements,preferably yarns, manufactured from the above referred materials can beused for manufacturing the strands. It was observed that the braidedcore provides chains according to the present invention with asubstantially lower slippage which are especially suitable for ropescomprising high strength yarns.

Methods of Measuring

-   -   Intrinsic Viscosity (IV) is determined according to        ASTM-D1601/2004 at 135° C. in decalin, the dissolution time        being 16 hours, with DBPC as anti-oxidant in an amount of 2 g/l        solution, by extrapolating the viscosity as measured at        different concentrations to zero concentration. There are        several empirical relations between IV and Mw, but such relation        is highly dependent on molar mass distribution. Based on the        equation M_(w)=5.37*10⁴ [IV]^(1.37) (see EP 0504954 A1) an IV of        4.5 dl/g would be equivalent to a M_(w) of about 422 kg/mol.    -   Tensile properties, i.e. tenacity and modulus were determined on        elongated elements as specified in ASTM D885M, using a nominal        gauge length of the fibre of 500 mm, a crosshead speed of        50%/min and Instron 2714 clamps, of type Fibre Grip D5618C. For        calculation of the strength, the tensile forces measured are        divided by the titre, as determined by weighing 10 meter of        fibre; values in GPa are calculated assuming the natural density        of the polymer, e.g. for UHMWPE is 0.97 g/cm³.    -   Breaking strength of the chains is determined on dry samples        using a horizontal tensile tester with a max load capacity of        15,000 kN at a temperature of approximately 21 degree C., and at        a rising force velocity of 250 kN/min. The chains were tested        using D-shackles with a diameter of the shackle of 95 mm (<1        MTex) and 220 mm (>1 MTex). The D-shackles are arranged in an        orthogonal configuration for the comparative chains and in a        parallel configuration for chain of the Example.    -   The melting temperature (also referred to as melting point) of        polymer is determined by DSC on a power-compensation PerkinElmer        DSC-7 instrument which is calibrated with indium and tin with a        heating rate of 10° C./min. For calibration (two point        temperature calibration) of the DSC-7 instrument about 5 mg of        indium and about 5 mg of tin are used, both weighed in at least        two decimal places. Indium is used for both temperature and heat        flow calibration; tin is used for temperature calibration only.    -   Chain tenacity was calculated by dividing the breaking strength        of the chain by the titer of the 2 legs of the braided cores.        Covers or coatings are disregarded when measuring the titer.    -   Efficiency is determined by dividing the tenacity of the        chain-link or chain by the tenacity of the load bearing yarn or        yarns.

EXAMPLES AND COMPARATIVE EXPERIMENT

Comparative Experiments

The chain-links of the comparative experiments are constructed accordingto the example as disclosed in WO2013/186206 whereby for comparabilitythe load bearing Dyneema® SK75 in the narrow weave was substituted byDyneema® DM20, a 1760 dtex yarn having a tenacity of 32.0 cN/dtexproduced and supplied by DSM Dyneema, The Netherlands. This narrowweave, or strip, employed in the comparative examples has a titer of272800 dtex and a nominal breaking strength of about 39 kN.

Comparative Experiment 1 and 2 were constructed by interlacing 3chain-links produced according to the comparative experiment inWO2013/186206, each of the 3 chain-links consisting of 8 and 12 turns ofthe DM20 narrow weave respectively, the 2 ends of each narrow weave ofeach chain-link being stitched together. Further properties and themaximum break load (MBL) of the 2 chains are reported in Table 1.

In Comparative Experiment 3, a chain according to Example II of documentWO2008/089798 has been produced. The chain had 4 engaging loops of 16Dyneema® SK75 yarns of 1760 dtex, produced and supplied by DSM Dyneema.This chain was fixed by air-splicing. Accordingly, each loop was formedfrom an air-spliced multifilament yarn bundle of 16×1760 dtex (28160dtex) with a diameter of about 4 mm and a theoretical strength of 9856 Nof the yarn bundle. Further properties and the maximum break load (MBL)of the chain are reported in Table 1.

Examples Example 1

A primary strand was braided from a total of 12 sub-strands, eachsub-strand consisting of 7×15 Dyneema DM20 1760 dtex yarns as employedfor the narrow weave of the Comparative Examples. Accordingly, theprimary strand was a braided rope construction of 12×7×15×1760 dtex(2217600 dtex) with a diameter of about 20 mm and a strength of 400 kN.A single length of about 20 m of said primary strand was used toconstruct a first chain-link by starting from an end of the 20 m primarystrand and forming a loop of about 3 m length (1 m diameter). With theremainder of the primary strand a total of 11 further loops were formedalong the first circle in such a way that the 12 loops form a firstTurk's head braided chain link construction from these 12 loops of thesingle primary strand whereby the pitch of the braid was about 10. Thetwo free ends of the primary strand were buried inside the Turk's headbraided chain-link construction. An alternative description of thebraided chain-link would be a 12-lead 4-bight Turk's head braid. Thechain link 10 formed of the Turk's head braided rope in the mannerdescribed above is shown in FIG. 1 .

The second and third chain-links were formed from 2 additional 20 mlengths of the primary strand in a process as described for the firstchain-link with the difference that the first loop and the further loopswere passing through the center of the first chain-link, hence forming achain consisting of 3 interlaced chain-links. The chain was subjected toa break load test. The primary strand (20 mm rope) broke twice withoutshowing substantial slip of the deteriorated chain-link. Even with theprimary strand fractured in 3 sections, the chain-link retained itstotal strength. The chain failed upon the third breakage of the primarystrand of one of it links. Further properties and the maximum break load(MBL) of the chain of Example 1 are reported in Table 1.

Example 2

A chain construction similar to the one of Example 1 was prepared withthe difference that the braided primary strand was braided from 12sub-strands each sub-strand consisting of only 4 Dyneema DM20 1760 dtexyarns resulting in a braided rope construction of 84480 dtex with adiameter of about 5 mm and a strength of about 20 kN. From said primarystrand braided chain-links with a diameter of about 0.3 m have beenprepared, starting from about 4 m of said primary strand for eachchain-link. Further details and MBL of the chain are reported in Table1.

Example 3

A chain similar to the chain of Example 2 was prepared and furthercoated by impregnating it with an aqueous suspension of a very-lowdensity polyethylene plastomer commercially available as Queo® (supplierBorrealis GmbH), dried for 24 hours at room temperature, resulting in aweight increase of about 20 wt %. Subsequently each of the braidedchain-links was heat set for 7 minutes and 120° C. at 2 t load (about10% of the MBL of the link). Details and break performance of the chainis provided in Table 1.

TABLE 1 Maximum break load and tenacity of chains Turns 2 legs of coresMBL Chain tenacity Basic strand [tex] (Loops) Legs [Mtex] [kN] [N/tex]Comp. 1 Weave: 27280 8 2 0.436 217.1 0.50 Comp. 2 Weave: 27280 12 20.655 329.8 0.50 Comp. 3 MF* Yarn: 176 16 2 0.005632 2.8 0.50 Example 1Rope: 221760 12 2 5.32 3081 0.58 Example 2 Rope: 8448 12 2 0.203 137.250.67 Example 3 Rope: 8448 12 2 0.203 166.4 0.86 MF* Yarn = multifilamentyarn (tex)

The invention claimed is:
 1. A chain comprising: a plurality ofinterconnected chain links, wherein at least one of the chain linkscomprises a Turk's head braided core comprising at least two consecutiveturns of at least one primary strand, wherein the at least one primarystrand comprises polymeric elongated elements having a tenacity of atleast 1.0 N/tex.
 2. The chain according to claim 1, wherein the at leastone primary strand is a tendon of parallel polymeric yarns.
 3. The chainaccording to claim 1, wherein the at least one primary strand is abraided, twisted or laid rope.
 4. The chain according to claim 1,wherein the Turk's head braided core comprises a cross-section which iscomprised of a number of cross-sections of the at least one firstprimary strand.
 5. The chain according to claim 1, wherein the Turk'shead braided core comprises at least three consecutive turns of the atleast one primary strand.
 6. The chain according to claim 1, wherein theTurk's head braided core comprises a plurality of primary strands,wherein the Turk's head braided core comprises at least two consecutiveturns of each of the plurality of primary strands.
 7. The chainaccording to claim 6, wherein each of the plurality of primary strandscomprises a plurality of polymeric elongated elements, and wherein eachof the polymeric elongated elements is formed of the same type ofpolymer.
 8. The chain according to claim 7, wherein at least one andanother of the plurality of polymeric elongated elements differ by atleast one property selected from the group consisting of material,tenacity, yarn titer, filament titer and creep rate.
 9. The chainaccording to claim 1, wherein the polymeric elongated elements of the atleast one primary strand have a tenacity of at least 1.2 N/tex.
 10. Thechain according to claim 1, wherein the at least one primary strand is abraided or laid primary strand having at least two terminal endsconnected together with a splice.
 11. The chain according to claim 1,wherein the at least one chain link comprises a cover, and whereineither (i) the at least one primary strand is sheathed with the cover,or (ii) the Turk's head braided core is sheathed with the cover.
 12. Thechain according to claim 1, wherein the polymeric elongated elements areat least partially coated with a thermoset or thermoplastic polymer. 13.The chain according to claim 1, wherein the Turk's head braided core hasa cross-section of between 5 mm² and 5 dm².
 14. The chain according toclaim 1, wherein the chain has a tenacity of at least 0.55 N/tex. 15.The chain according to claim 1, wherein the chain has a static strengthof at least 300 kN.
 16. The chain according to claim 1, wherein theTurk's head braided core comprises at least four consecutive turns ofthe at least one primary strand.
 17. The chain according to claim 1,wherein the Turk's head braided core comprises at least six consecutiveturns of the at least one primary strand.
 18. The chain according toclaim 1, wherein the Turk's head braided core has at most 24 consecutiveturns of the at least one primary strand.
 19. The chain according toclaim 18, wherein the Turk's head braided core has at most 18consecutive turns of the at least one primary strand.
 20. The chainaccording to claim 18, wherein the Turk's head braided core has at most12 consecutive turns of the at least one primary strand.
 21. The chainaccording to claim 1, wherein the Turk's head braided core comprises aplurality of primary strands, and wherein the Turk's head braided corecomprises at least six consecutive turns of each of the plurality ofprimary strands.
 22. The chain according to claim 21, wherein each ofthe plurality of primary strands comprises a plurality of polymericelongated elements comprising polymeric yarns of the same type.
 23. Thechain according to claim 1, wherein the polymeric elongated elements ofthe at least one primary strand have a tenacity of at least 2.0 N/tex.24. The chain according to claim 1, wherein the polymeric elongatedelements of the at least one primary strand have a tenacity of at least2.5 N/tex.
 25. The chain according to claim 12, wherein the thermosetand the thermoplastic are polymer silicone resins and plastomers,respectively.
 26. The chain according to claim 1, wherein the Turk'shead braided core has a cross-section between 10 mm² and 3 dm².
 27. Thechain according to claim 1, wherein the Turk's head braided core has across-section between 50 mm² and 100 cm².
 28. The chain according toclaim 1, wherein each of the polymeric elongated elements is anultrahigh molecular weight polyethylene (UHMWPE) yarn having a tenacityof at least 1.8 N/Tex.
 29. The chain according to claim 1, wherein eachof the polymeric elongated elements is an ultrahigh molecular weightpolyethylene (UHMWPE) yarn having a tenacity of at least 2.5 N/Tex. 30.The chain according to claim 1, wherein the chain has a tenacity of atleast 0.60 N/tex.
 31. The chain according to claim 1, wherein the atleast one primary strand is a woven strand.
 32. The chain according toclaim 1, wherein the polymeric elongated elements comprise fibers madefrom organic synthetic material selected from the group consisting ofpolyolefins, polyamides, polyaramides; poly(tetrafluoroethylene) (PTFE),poly(p-phenylene-2, 6-benzobisoxazole) (PBO), liquid crystal polymers,poly{2,6-diimidazo-[4,5b-4′,5′e]pyridinylene-1,4(2,5-dihydroxy)phenylene},polyesters, polyvinyl alcohols and polyacrylonitriles.
 33. The chainaccording to claim 1, wherein the polymeric elongated elements comprisefibers made from organic synthetic material selected from the groupconsisting of polypropylene (PP), polyethylene (PE), ultrahigh molecularweight polyethylene (UHMWPE), poly(p-phenylene terephthalamide),copolymers of para hydroxybenzoic acid and para hydroxynaphtalic acid,poly(hexamethyleneadipamide), poly(6-aminohexanoic acid); poly(ethyleneterephthalate), poly(butylene terephthalate), and poly(1,4cyclohexylidene dimethylene terephthalate).